docs: def walk(self, parent=None):
          """Generator that yields pages in infix order
  
          Args:
              parent: hotdoc.core.tree.Page, optional, the page to start
                  traversal from. If None, defaults to the root of the tree.
  
          Yields:
              hotdoc.core.tree.Page: the next page
          """
          if parent is None:
              yield self.root
              parent = self.root
  
          for cpage_name in parent.subpages:
              cpage = self.__all_pages[cpage_name]
              yield cpage
              for page in self.walk(parent=cpage):
                  yield page